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- Title
Three-dimensional instabilities in oscillatory flow past elliptic cylinders.
- Authors
Gallardo, José P.; Andersson, Helge I.; Pettersen, Bjørnar
- Abstract
We investigate the early development of instabilities in the oscillatory viscous flow past cylinders with elliptic cross-sections using three-dimensional direct numerical simulations. This is a classical hydrodynamic problem for circular cylinders, but other configurations have received only marginal attention. Computed results for some different aspect ratios Δ from 1 : 1 to 1 : 3, all with the major axis of the ellipse aligned in the main flow direction, show good qualitative agreement with Hall's stability theory (J. Fluid Mech., vol. 146, 1984, pp. 347-367), which predicts a cusp-shaped curve for the onset of the primary instability. The three-dimensional flow structures for aspect ratios larger than 2 : 3 resemble those of a circular cylinder, whereas the elliptical cross-section with the lowest aspect ratio of 1 : 3 exhibits oblate rather than tubular three-dimensional flow structures as well as a pair of counter-rotating spanwise vortices which emerges near the tips of the ellipse. Contrary to a circular cylinder, instabilities for an elliptic cylinder with sufficiently high eccentricity emerge from four rather than two different locations in accordance with the Hall theory.
- Subjects
ELLIPTIC curves; VISCOUS flow; FLUID flow; VISCOSITY; ASPECT ratio (Images)
- Publication
Journal of Fluid Mechanics, 2016, Vol 798, p371
- ISSN
0022-1120
- Publication type
Article
- DOI
10.1017/jfm.2016.319